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This paper aims to study the colour stability of chlorophyll and the effect of copper (II) nitrate – Cu(NO₃)₂ – as an additive in natural dye coating films after being exposed to ultraviolet-A (UV-A).

The natural dye was extracted from the leaves of Cassia alata L. using absolute ethanol as the solvent. The extract was divided into two parts and, one of it was added with 3 wt.% Cu(NO₃)₂ as an additive. The polymer blend of poly(methyl methacrylate) (PMMA) and acrylic polyol was used as the coating binder. Both parts of the dye with and without additive were mixed with the blended polymer in a specific ratio. The resulted mixtures were applied as coating films on glass substrates. The colour stability of the coating films on exposure to UV-A with the time of exposure was observed with Commission internationale de l’éclairage (CIE) L*a*b* colour coordinates. The hidden power by the means of reflectivity and glossiness of the coatings was also studied. Statistical standard deviation (STD) was used to analyse the data.

The test showed that the coating films containing Cu(NO₃)₂ had smaller colour differences, (ΔE*) indicating higher colour stability. The analysis on hidden power also showed that the coating film with Cu(NO₃)₂ was 1.6 times more stable than the film without additive. All the measurements in this study were observed within 35 days of duration.

This paper implies the potential of using natural dye extracted from Cassia alata L. leaves as a stable dye colourant for coating applications.

The coating film developed in this study is suitable for glass substrate applications.

A new method of preparing solvent-based coating film from PMMA–acrylic polyol with chlorophyll colourant is introduced in this study.

This paper aims to discuss about the benefits of Cu(NO₃)₂ applied in coating paint film that consists of plant extract from Cassia Alata. Cu(NO₃)₂ has been added to the coating paint film as a colour stabilizer and as an antifungal property by forming a zone of inhibition towards fungal growth.

The coating paint film resin consists of a mixture of poly (methyl methacrylate) (PMMA) and acrylic polyol. The coating paint film’s performances were observed in terms of visible optical and physical appearance.

When exposed to the fungus Trichoderma Sp., a zone of inhibition of 208 mm² was formed around the coating paint film and therefore it gave the coating paint films an antifungal property. The commission internationale de l’éclairage (CIE) L*a*b* colour coordinate system was used to identify the colour changes in the coating paint film and it was found that the addition of Cu(NO₃)₂ to the coating paint film has a better colour stability, as it has a lower standard deviation (STD) value of 6.46 than the pure dye coating paint film of 8.95. The gloss of coating paint film with the addition of Cu(NO₃)₂ was found to be have a more stable gloss based on its smaller STD value at both angles taken at 20° and 60°.

The Cassia Alata plant has different amount of antifungal properties based on location its growth.

The coating paint film developed in this study is suitable for indoor applications.

The plant extract from the Cassia Alata gives the coating paint film an antifungal property.

The purpose of this paper is to study the colour stability and water content resistivity of the green colour coating paint film (consisting of chlorophyll) during exposure to ultraviolet A (UV-A).

The natural green dye was prepared by immersing Cassia alata L. leaves in absolute ethanol. The extract was prepared in two batches of dye samples where one of it was a pure dye and the other was added with 3 Wt. % Cu(NO₃)₂ as an additive. Polymer blend as a binder was prepared by mixing poly(methyl methacrylate) (PMMA) and commercial acrylic polyol. The blended polymer was mixed with the natural dye in a specific ratio and applied as coating paint film on glass panel surfaces. The visible spectrum stability (colour stability) and water content resistivity of the coating paint films during exposure to UV-A were monitored.

Addition of Cu(NO₃)₂ had improved the colour stability of the coating paint film. Fourier transform infrared spectroscopy analysis showed that both coating paint films do not absorb water and are resistive to water content.

The ability of Cu(NO₃)₂ as an colour stability additive to the natural green dye applied in the coating paint film.

The coating paint film developed in this work is suitable to be applied on glass substrates.

The colour stability of the coating paint film was analysed by using the reflectance spectrum.

In this paper, the authors show that ecological restoration potential through natural regeneration of degraded tropical rainforest is possible. This is significant because at present most of the tropical forest of the world, including of Bangladesh, are degraded.

Regeneration status of Chunati Wildlife Sanctuary (CWS) was assessed through stratified random sampling method using sample plots of 5 × 5 m in size covering 269 sample plots.

A total of 3,256 regenerating seedlings/saplings of 105 species belonging to 35 families were recorded from CWS. From regenerating tree species, maximum (37.83) family importance value (FIV) index was found for Euphorbiaceae followed by Myrtaceae (18.03). Maximum importance value index (IVI) was found for Aporosa wallichii (21.62) followed by Grewia nervosa (16.41). Distribution of seedlings into different height classes of regenerating tree species was also calculated.

Forest scientists are working to find out the best nature-based solution for ecological restoration of tropical rainforests to attain climate resilient ecosystem in a sustainable way. Tropical rain forest has huge plant diversity, and we find that ecological restoration is possible through natural regeneration from its rich soil seed bank. Natural regeneration is the best nature-based solution for sustainable management of the forest.

The authors believe that the findings presented in our paper will appeal to the forest and environmental scientists. The findings will allow readers to understand degraded tropical hill forest ecosystem and its management strategy.

The authors believe that this manuscript will give a clear picture about degraded tropical hill forest ecosystem and its genetic composition, diversity and soil seed bank status to apply appropriate management strategy.